Chip resistors in general include an insulating substrate and terminal electrodes for soldering, where the substrate appears to be an elongated rectangle as viewed in plan, and each of the terminal electrodes is formed on one of the two end surfaces adjacent to the shorter sides of the elongated rectangle.
FIG. 15 is a perspective view showing a typical chip resistor. The chip resistor 101 includes an insulating substrate 102 whose upper surface is formed with upper electrodes 103 and 104 disposed at the ends of the upper surface spaced from each other in the longitudinal direction of the substrate. The upper surface of the substrate 102 is also formed with a resistor film 105 extending in the longitudinal direction of the insulating substrate 102. The ends of the resistor film 105 overlap the upper electrodes 103 and 104, respectively, to be electrically connected to the electrodes 103, 104. One of the end surfaces of the insulating substrate 102 is formed with a terminal electrode 106 electrically connected to the upper electrode 103, while the other end surface of the substrate is formed with a terminal electrode 107 electrically connected to the upper electrode 104. The chip resistor 101 is mounted on e.g. a printed circuit board by soldering the terminal electrodes 106 and 107.
In the chip resistor 101, the insulating substrate 102 is prone to thermally expand or contract in its longitudinal direction by the heat generation at the resistor film 105. As noted above, the terminal electrodes 106 and 107 of the chip resistor 101 are provided on the longitudinally spaced end surfaces, and the terminal electrodes 106 and 107 are soldered to e.g. a printed circuit board. Thus, a relatively large stress due to the thermal expansion or contraction is repetitively applied to the soldered portions of the terminal electrodes 106 and 107. Further, since the area for soldering is narrow, defective soldering such as unexpected detachment of the terminals may occur.
In light of the above, a chip resistor has been proposed, in which terminal electrodes for soldering are provided on the relatively long side surfaces of an insulating substrate that appears to be an elongated rectangle as viewed in plan.
FIG. 16 is a perspective view showing a chip resistor including terminal electrodes formed on the long side surfaces. In the chip resistor 201, the upper surface of the insulating substrate 202 is formed with upper electrodes 203 and 204 along two edges spaced from each other in a direction perpendicular to the longitudinal direction. The upper surface of the insulating substrate 202 is further formed with a resistor film 205 extending in the direction perpendicular to the longitudinal direction of the substrate 202. The ends of the resistor film 205 overlap the upper electrodes 203 and 204, respectively, to be electrically connected to the electrodes 203, 204. One of the long side surfaces of the insulating substrate 202 is formed with a terminal electrode 206 electrically connected to the upper electrode 203, while the other long side surface of the insulating substrate 202 is formed with a terminal electrode 207 electrically connected to the upper electrode 204. The chip resistor 201 is mounted on e.g. a printed circuit board by soldering the terminal electrodes 206 and 207.
In the chip resistor 201, the thermal expansion or contraction in the direction perpendicular to the longitudinal direction of the substrate 202 is smaller than the thermal expansion or contraction in the longitudinal direction. Further, with the terminal electrodes 206 and 207 provided on the long side surfaces, the soldering area of the terminal electrodes 206 and 207 is considerably increased. Thus, for the chip resistor 201, the likelihood of unexpected detachment at the soldered portions is significantly reduced.